UNIT 1: RENAL FUNCTION Flashcards
glucose, amino acids, salts
active, proximal
chloride
active, ascending loop of henle
sodium
proximal and distal ct
water
passive, pct, descending loop of henle, collecting duct
urea
PASSIVE (WUS) = pct, ascending loop pf henle
sodium
ascending loop of henle
Responsible for removal of waste products and
reabsorption of nutrients
cortical 85%
Have longer loops of Henle that extend deep
into the medulla of the kidney. Their primary
function is concentration of the urine.
juxtamedullary 15%
Human Kidney receives 25% of the blood
TRUE
Blood enters the nephron via
AFFERENT ARTERIOLE
Blood flows through the glomerulus and into the
EFFERENT ARTERIOLES
The varying sizes of these arterioles help to create
the _________ differential important for
glomerular filtration and to maintain consistency of
glomerular capillary pressure and renal blood flow
hydrostatic pressure
smaller size of the__________ the glomerular capillary
pressure.
efferent arteriole increases
Blood from the efferent enters the
peritubular capillaries
for immediate reabsorption
vasa recta
surround the proximal and
distal convoluted tubules, providing for the immediate reabsorption of essential substances from the fluid in the proximal convoluted tubule
peritubular capillaries
final adjustment
of the urinary composition in the ___________
distal convoluted
tubule.
located adjacent to the ascending
and descending loops of Henle in juxtamedullary
nephrons. In this area, the major exchanges of water
and salts take place between the blood and the
medullary interstitium.
VASA RECTA
Total Renal Blood Flow:
1200 ml/min
Total Renal Plasma Flow
600-700 ml/min
consists of a coil of approximately eight capillary
lobes, the walls of which are referred to as the
glomerular filtration barrier.
GLOMERULUS
glomerulus is located within
_________ which forms the beginning of renal tubule.
Bowman’s capsule
Nonselective filter of plasma substances (molecular
weight of less than 70,000)
glomerulus
Factors influencing filtration process:
■ Cellular Structure of the Glomerulus
■ Hydrostatic pressure
■ Oncotic Pressure
■ Feedback mechanism of RAAS
(renin-angiotensin-aldosterone system).
Plasma filtrate must pass:
- Capillary wall membrane
- Basement membrane (basal lamina)
- Visceral epithelium of the Bowman’s Capsule
The endothelial cells of the capillary wall differ from those in other capillaries by ________ and are referred to as fenestrated.
containing pores = FENESTRATED
increase capillary permeability but
do not allow passage of large molecules and blood cells.
PORES
Further restriction of large molecules:
- basement membrane
- thin membranes covering the filtration slits (podocytes)
barrier contains a___________ that repels
molecules with a negative charge even though they are small enough to pass through the three layers of the barrier. The shield is very important because_________ (the primary protein associated with renal disease) has a negative charge and would easily pass through the barrier.
shield of negativity; albumin
If it were not for the shield of negativity, all
routine urines would have positive reagent strip readings for protein/albumin.
TRUE
Results from the smaller size of the efferent arterioles and the
glomerular capillaries
glomerular pressure
INCREASE IN PRESSURE: _______ in surface area
DECREASE
By increasing or decreasing the size of the afferent and efferent
arterioles, an __________ maintains the glomerular blood pressure at a relatively constant rate regardless of fluctuations in systemic blood pressure
autoregulatory mechanism within the
juxtaglomerular apparatus
dilation happens in
afferent
constriction of the
efferent arterioles
prevents a marked decrease in blood flowing through the
kidney, thus preventing an increase in the blood level of toxic
waste products.
Dilation of the afferent arterioles
and constriction of the efferent arterioles when blood pressure
drops
● Regulates the blood flow to and within the glomerulus
Respond to changes in the blood pressure and plasma sodium content that are monitored by the _______which consists of the juxtaglomerular cells in the afferent arteriole and the macula densa of the distal convoluted tubule.
RAAS
juxtaglomerular
apparatus
______ plasma sodium content decreases
water retention within the circulatory system, resulting in a
______overall blood volume and subsequent decrease in blood pressure.
decreased
When the ______ senses such
changes, a cascade of reactions within the RAAS occurs.
macula densa
an enzyme produced by the juxtaglomerular cells
RENIN
renin is secreted and reacts with the blood-borne substrate
angiotensinogen
produce the inert hormone angiotensin I.
angiotensinogen
As angiotensin I passes through the alveoli of the lungs, __________ changes it to the active form angiotensin II.
angiotensin-converting enzyme (ACE)
corrects renal blood flow in the following
ways:
1. causing vasodilation of the afferent arterioles and
constriction of the efferent arterioles
2. stimulating reabsorption of sodium and water in the proximal convoluted tubules,
3. triggering the release of the sodium-retaining
hormone aldosterone by the adrenal cortex and
antidiuretic hormone by the hypothalamus
angiotensin II
As systemic blood pressure and plasma sodium content ________, the secretion of renin _________
increases, decreases
Because this filtration is
______, the only difference between the compositions
of the filtrate and the plasma is the _______
nonselective, absence of plasma
protein, any protein-bound substances, and cells.
sodium reabsorption
PROXIMAL
triggers antidiuretic hormone release by the hypothalamus to stimulate water reabsorption inthe collecting duct
RAAS
The body cannot lose 120 mL of water-containing essential substances every minute. Therefore, when the _______ enters the _______ convoluted tubule, the
nephrons, through cellular transport mechanisms, begin reabsorbing these essential substances and water.
plasma ultrafiltrate; proximal convoluted tubule
Substances are removed from the glomerular filtrate and returned to the blood
tubular reabsorption
cellular mechanism
maximal reabsorptive capacity
renal threshold
tubular reabsorption
Plasma concentration where the active transport stops
renal threshold
For glucose, the plasma renal
threshold is ________ and
glucose appears in the urine when
the plasma concentration reaches
this level.
160 to 180 mg/dL
distal convoluted tubule sodium reabsorption
aldosterone
collecting duct water resorption
ADH
proximal convoluted tubule sodium reabsorption
angiostenin II
the substance to be reabsorbed must combine with a carrier protein contained in the membranes of the
renal tubular epithelial cells
active transport
The electrochemical energy created by this interaction transfers the
substance across the cell membranes and back into
medulla
responsible for the reabsorption of
glucose, amino acids, and salts in the proximal
convoluted tubule, chloride in the ascending loop of
Henle, and sodium in the distal convoluted tubule.
glucose, amino acids and salts = proximal
chloride= ascending
sodium = distal
ACTIVE TRANSPORT
the movement of molecules across a membrane as a result of differences in their concentration or electrical potential on opposite sides of the membrane.
passive transport
physical differences in passive transport
gradients
Passive reabsorption of water takes place in all parts
of the nephron except the
ascending loop of Henle KASI SA DESCENDING SHA
Urea is passively reabsorbed in the proximal convoluted tubule and the ascending loop of Henle, and passive reabsorption of sodium accompanies the active transport of chloride in the ascending loop.
urea = PCT, ASCENDING
sodium= ASCENDING
Glucose appearing in the urine of a person
with a normal blood glucose level is the result of ________
tubular damage
Renal concentration begins in the
descending and ascending loop of henle
Water is removed by osmosis in the
descending
Na and Cl are reabsorbed in the
ascending loop of henle
Excessive reabsorption of water as the filtrate passes through
the highly concentrated medulla is prevented by the
water-impermeable walls of the
ascending loop
Selective reabsorption process
countercurrent mechanism
Serves to maintain the osmotic gradient of the medulla
○ Which is essential for the kidneys to
concentrate the urine effectively
countercurrent mechanism
Ang nakapalibot sa loop of Henle
vasa recta
Ang nakapalibot sa PCT at DCT
peritubular capillaries
Maintenance of this osmotic gradient is essential for
the final concentration of the filtrate when it reaches the collecting duct.
countercurrent mechanism
Reabsorption of sodium continues in the distal
convoluted tubule, but it is now under the control of
the hormone
aldosterone
The final concentration of the filtrate through the reabsorption of
water begins in the late distal convoluted tubule and continues in the
collecting duct. Reabsorption depends on the osmotic gradient in the
medulla and the hormone
vasopressin or ADH
high body hydration =
low ADH, high urine volume
Involves the passage of substances from the blood in the
peritubular capillaries to the tubular filtrate
tubular secretion
two major functions of tubular secretion
- Elimination of waste products not filtered by the
Glomerulus - Regulation of acid base balance through secretion of Hydrogen ions
The major site for removal of these non filtered substances is
proximal convoluted tubule
is an active process that involves the
movement of substances against their concentration gradient using specific transporters or ion channels.
tubular secretion
Measures the rate in milliliters per minute at which the
kidneys are able to remove a filterable substance from the
blood
Glomerular filtration tests
Helpful in determining the stage of ckd and assessing kidney function
glomerular filtration tests
Characteristics of Substance to be tested
Should neither be reabsorbed or secreted by the
tubules
Substance must be stable for 24 hours
Plasma level should be constant
Substance should be available in the body
Availability of the tests to analyze the substance
Requires 2-hour sample
earliest clearance test
sodium
urea clearance test
polymer of fructose
extremely stable, not reabsorbed
infused at constant rate
inulin clearance test
are the primary substances
used in clearance tests.
creatinine, beta2-microglobulin, cystatin C,
and possibly radioisotopes
Requires 24-hour sample
Endogenous procedure for evaluating glomerular filtration
A test that requires an infused substance is termed an exogenous procedure and is seldom the method of choice if a suitable test substance is already present in the body (endogenous procedure).
creatine clearance test
disadvantages or creatine clearance test
Some creatinine are secreted by tubules
○ Chromogens in human plasma react in the chemical analysis
○ Medications including gentamicin, cephalosporins, and cimetidine (Tagamet), inhibit tubular secretion of
creatinine, thus causing falsely low serum levels
○ Bacteria breakdown urinary creatinine levels
○ Diet can influence the result
the increased intake of meat can
raise the urine and plasma levels
of creatinine during the 24-hour
collection period.
TRUE
at the 12th hour
midpoint
at the 23rd hour
endpoint
reference range male
107-139 ml/min
reference range female
87-107 ml/min
Used for routinely screening patients as part of a metabolic
profile and to monitor patients already diagnosed with renal
disease or at risk for renal disease
estimated glomerular filtration rates
The most frequently used formula is called
Modification of Diet in Renal Disease (MDRD) study.
Measurement of serum cystatin C has been shown to provide a good procedure for screening and monitoring GFR.
cystatin c
○ Produced by all nucleated cell at constant rate
○ Filtered readily by the glomerulus and reabsorbed and
broken down by the renal tubular cells
cystatin c clearance test
Therefore, no cystatin C is secreted by the
tubules, and the serum concentration can be
directly related to the GFR.
Advantage: Independent of Muscle Mass
Recommended: Pediatric patients, Elders, People with Diabetes, Critically-ill
TRUE
Dissociates from human leukocyte antigen at constant
rate
○ Removed rapidly from the plasma by glomerular
filtration
Most sensitive indicator of a decrease in GFR
beta 2 microglobulin
Principle: salts and water are reabsorbed in the tubules
tubular reabsorption test
Used to determine the ability of the tubules to
reabsorb essential salts and water that have been
non-selectively filtered by the glomerulus
concentration test
compare day and night of specific
gravity. It should be at least 1.018 specific gravity.
mosenthal test
patient is deprived of water then
measures specific gravity. It should be atleast 1.025 if
the patient is already deprived of water for 16 hours
fishberg test
Measures only the number of particles in a solution
Performed for a more accurate evaluation of renal
concentrating ability
osmolality
Measurement of freezing point depression was the
first principle incorporated into clinical osmometers
These osmometers determine the freezing point of a solution by supercooling a measured amount of
sample to approximately 27°C. The supercooled
sample is vibrated to produce crystallization of water
in the solution.
freezing-point osmometers
Historical test
Standardization and interpretation of PSP results are difficult
Phenolsulfonpthalein Excretion Test (PSP)
Most commonly associated with the tubular secretion
and renal blood flow
P-aminohippuric acid (PAH)
dye test; infused then measured the
one secreted. Because dye should be secreted.
indigo carmine test
Titratable Acidity and Urinary Ammonia are
tests to determine the tubular reabsorption of the kidneys.
FALSE, TUBULAR SECRETION DAPAT
